The present invention relates to a generator of the clockwork type and to a clockwork movement fitted with such a generator, in particular for a wristwatch.
The use of batteries or accumulators is a factor which limits the features of the apparatus, for all applications, and in particular for a watch. Indeed, changing or recharging the batteries or accumulators affects the availability and reliability of the watch.
In this context, the conventional mechanical watch has a certain advantage in watchmaking know-how: such a watch is permanently available. The recharge of powerxe2x80x94which is purely mechanicalxe2x80x94is achieved simply by rewinding the watch mechanism.
This type of watch uses a manual or automatic winding device generally coupled to a regulating device commonly called a xe2x80x9cSwiss lever escapementxe2x80x9d. It is difficult to obtain a high level of precision with this regulating device. This system is also relatively expensive.
The other large family concerns the conventional quartz watch. A battery simultaneously powers an electric motor and a device for regulating the working of the motor. The motor rotation is controlled by a nominal frequency supplied by a quartz. This provides a high level of precision for the time indication. However, this device is relatively noisy since the forward movement of the second wheel is intermittent and the battery has to be changed periodically.
New types of watch have been made combining the two aforecited systems and exploiting their respective advantages. In these constructions, mechanical power storage has been associated with quartz regulation, supplied with electric power by a generator driven by a mechanical part coupled with a power storage spring.
The article by MM Born, Dinger and Farine xe2x80x9cSalto-An automatically wound mechanical movement with the precision of a quartz movementxe2x80x9d which appeared in the Swiss Chronometry Society publication xe2x80x9cSSC study days 1997xe2x80x9d, pages 55 to 63 may also be cited as the corresponding state of the art.
The arrangement of the generator according to this prior art is illustrated in FIG. 1 annexed hereto, showing a top view of a partially assembled clockwork movement, and in FIG. 2 annexed hereto, which is a transverse cross-section of FIG. 1. This generator includes a rotor with two flanges 8 arranged on either side of three flat coils 11 forming the stator and offset by 120xc2x0 with respect to each other relative to the rotor axis, in the same orthogonal plane as the latter.
Six magnets 9 are fixed radially and at regular intervals on each flange 8, facing coils 11. Two consecutive or facing magnets 9 have opposite polarity. A printed circuit 6 is secured to plate 4 and is used as a support for coils 11.
Electric circuit 10, which has a low power consumption, is powered by an electric generatorxe2x80x94formed by the shaft assembly of rotor 5, flanges 8, magnets 9 and coils 11xe2x80x94driven via the kinematic connection 3 by barrel device 2. The mechanical power stored in barrel 2 thus drives the rotor. The passage of magnets 9 in proximity to coils 11 generates a substantially sinusoidal induced voltage at the terminals of coils 11.
FIG. 3 annexed hereto demonstrates schematically the fact that the assembly of the monoblock rotorxe2x80x94formed of parts 5, 8 and 9 in the completed device is currently achieved by inserting shaft 5 laterally between two fixed coils 11. The monoblock rotor cannot be inserted vertically since the three coils 11 are fixed and flanges 8 located on either side of these coils must partially cover them. As is clear in particular from FIGS. 2 and 3 of the aforecited document, coils 11 have a space, referenced Dmin in FIG. 3 annexed hereto, at least as wide as rotor shaft 5, having a diameter D at its centre, to allow the shaft to be inserted laterally until it is placed definitively at the centre of the three coils. Because of the space thereby arranged between the three coils 11 offset angularly by 120xc2x0, a mediocre covering of coils 11 is obtained from magnets 9, which causes a drop in the yield of the micro-generator, and a relatively large space requirement. In other words, the number of turns of coils 11 superposed onto flanges 8 carrying magnets 9 at their periphery is limited.
The object of the invention is to overcome these drawbacks. The invention therefore concerns a generator of the clockwork type including on the one hand a rotor including two flanges carried by a shaft, this shaft and the flanges being fixed in rotation when operating, magnets, in even numbers, being fixed to each flangexe2x80x94two consecutive or facing magnets having opposite polarityxe2x80x94and including on the other hand a stator formed of at least three coils with axes parallel to that of the rotor, and arranged on a support, these coils being arranged between the two flanges fitted with magnets after the generator is assembled and arranging between them a sufficient central space for said rotor shaft. This generator is characterised in that the coil support is formed of at least two distinct parts which can be assembled with the rotor independently of each other and each carrying at least one coil, and in that means for electrically connecting said at least two parts are provided, the distance separating any two adjacent coils after assembly of the generator being less than diameter D of the rotor shaft.
According to a second embodiment of the invention, the generator of the clockwork type is characterised in that the coil support includes two rigid or rigidified parts, each carrying a coil and a part able to be deformed materially connecting said rigid parts, said deformable part being elastically deformed upon assembly of the rotor to allow the lateral passage of said rotor shaft between two coils, the distance between any two adjacent coils after assembly of the generator being less than diameter D of the rotor shaft.
As a result of the features of the above mentioned first or second embodiment of the invention, it is possible to use the coupling space between the rotor magnets and the stator coils in an optimal manner. The diameter of the rotor shaft is no longer a limiting parameter for the dimensions of the stator coils. Therefore, the yield of the generator and/or the space requirement of the stator are improved.